Reconstructive bone and ligament surgery often involves drilling bone tunnels into skeletal members to attach connective elements such as ligament and tendon grafts, as well as various artificial replacements and/or attachments for articulated joints. Careful placement and subsequent drilling ensures maximum joint mobility from the resulting reconstruction.
A common anterior cruciate ligament (ACL) reconstruction technique involves the drilling of bone tunnels into the tibia and the femur in order to place an ACL graft in almost the same position as the torn ACL. The free ends of a suture loop are then passed through the tunnel of the tibia, up through the femoral tunnel, and then out through the skin of the thigh. The sutures of the graft are placed through the eye of the needle and the graft is pulled into position up through the tibial tunnel and then up into the femoral tunnel. The graft is held under tension as it is fixed in place using interference screws, spiked washers, buttons, posts and/or staples.
Anatomic placement of the ACL graft is critical to the success of the ACL reconstruction. In fact, the most commonly cited error in ACL reconstruction is nonanatomic tunnel placement, with an improperly placed femoral tunnel being the root cause in most cases. When the femoral tunnel is placed in a position that is too anterior, the result can be a graft that experiences constraint in flexion and laxity in extension. When the femoral tunnel is placed too posteriorly, a loss of fixation due to posterior wall blowout may be experience along with a constraint in extension due to nonisometric tunnel position. Placement of the femoral tunnel that is too central results in a graft that may not restore the rotational component of stability provided by the ACL, thereby leading to a persistently positive pivot shift, despite objective anterior/posterior stability.